A Study to Evaluate Pharmacokinetics, Pharmacodynamics and Tissue Concentrations of Epelsiban

This multi-cohort phase I study is designed to assess the pharmacokinetics (PK) and pharmacodynamics (PD) of oxytocin and to evaluate epelsiban (GSK557296) potential to reduce subendometrial contractractility induced by oxytocin in healthy female subjects. Additionally tissues concentrations of epelsiban will be determined from endometrial tissue biopsies. Data from this study will inform the identification of the doses of epelsiban to be used in future in-vitro fertilization (IVF) clinical studies. Expected number of subjects to be randomized are: Cohort 1- 10 subjects, Cohort 2a- 10 subjects for each epelsiban arm 25 milligrams (mg), 200mg, 5 for placebo, Cohort 2b- 10 subjects per arm with dose to be determined, cohort 3- 6 subjects. Cohorts 1 and 2 will be double blind (sponsor unblinded) placebo controlled cohorts. Cohort 3 will be an open label cohort, cohort 4 will be a double blind (sponsor unblinded) placebo controlled cohort.